DE102018133435A1 - DISASSEMBLY METHOD AND DISASSEMBLY DEVICE BASED ON A BASIC MATERIAL COMBINATION - Google Patents

Abstract

The present disclosure provides a decomposition method based on a base material combination. In the present disclosure, a scanned object is divided into a plurality of regions, the base material combinations used in each of the divided regions are different from each other, and the scanned object is re-divided according to the re-determined equivalent atomic number of each of its points until the change of the decomposition coefficient meets certain conditions. Thereby, a decomposition method based on dynamic base material combinations is realized, which reduces a decomposition error caused by improper selection of the base material combination, and improves the accuracy of decomposition and substance identification of the multi-energy CT.

Description

The present disclosure is based on Chinese Patent Application No. 201711432840.5 , filed on Dec. 26, 2017, the priority of which is claimed and the disclosure of which is fully incorporated by reference herein.

TECHNICAL AREA

The present disclosure relates to the field of radiation imaging, and more particularly relates to a decomposition method and a decomposition apparatus based on a base material combination.

BACKGROUND

A related X-ray dual energy CT imaging technique decomposes a damping coefficient function of a substance into a linear combination of damping coefficient functions of two known base materials and coefficients of the linear combination are unknown parameters to be solved. The decomposition of a scanned object uses a fixed set of dual base materials and a corresponding fixed set of attenuation coefficient functions. For example, water and bone can be selected as dual base materials in dual-energy medical CT.

SUMMARY OF THE INVENTION

• einen Erhaltungsschritt zum Erhalten von Zerlegungskoeffizienten und einer äquivalenten Atomzahl jedes Punkts eines abgetasteten Objekts;
• einen Bereichsunterteilungsschritt zum Unterteilen des abgetasteten Objekts in mehrere Bereiche gemäß der äquivalenten Atomzahl jedes Punkts des abgetasteten Objekts, wobei die Basismaterialkombinationen, die in jedem der unterteilten Bereiche verwendet werden, voneinander verschieden sind;
• einen Zerlegungskoeffizientenbestimmungsschritt zum Bestimmen von Zerlegungskoeffizienten jedes Punkts in dem Bereich in Bezug auf jeden der unterteilten Bereiche auf der Basis der in dem Bereich verwendeten Basismaterialkombination;
• einen Bestimmungsschritt für äquivalente Atomzahlen zum Bestimmen von äquivalenten Atomzahlen für alle Punkte im unterteilten Bereich in Bezug auf jeden der unterteilten Bereiche auf der Basis der bestimmten Zerlegungskoeffizienten aller Punkte im unterteilten Bereich und von Atominformationen aller Basismaterialien der in dem unterteilten Bereich verwendeten Basismaterialkombination dann, wenn die Änderung des Zerlegungskoeffizienten auf der Basis der Zerlegungskoeffizienten aller Punkte in allen unterteilten Bereichen nicht geringer ist als ein vorgegebener Schwellenwert; und
• einen Schleifendurchlaufschritt zum Durchlaufen des Bereichsunterteilungsschritts, des Zerlegungskoeffizientenbestimmungsschritts und des Bestimmungsschritts für äquivalente Atomzahlen in einer Schleife gemäß den bestimmten äquivalenten Atomzahlen jedes Punkts des abgetasteten Objekts, bis die Änderung des Zerlegungskoeffizienten auf der Basis der Zerlegungskoeffizienten aller Punkte in allen unterteilten Bereichen geringer ist als ein vorgegebener Schwellenwert.

One aspect of the present disclosure provides a decomposition method based on a base material combination comprising:

• a preserving step for obtaining decomposition coefficients and an equivalent atomic number of each point of a scanned object;
• a region dividing step for dividing the scanned object into a plurality of regions according to the equivalent atomic number of each point of the scanned object, the base material combinations used in each of the divided regions being different from each other;
• a decomposition coefficient determination step for determining decomposition coefficients of each point in the region with respect to each of the divided regions on the basis of the base material combination used in the region;
• an equivalent atomic number determining step of determining equivalent atomic numbers for all the divided region points with respect to each of the divided regions on the basis of the determined decomposition coefficients of all the divided region points and atomic information of all the base materials of the base material combination used in the divided region Change of the decomposition coefficient on the basis of the decomposition coefficients of all points in all the divided areas is not less than a predetermined threshold; and
• a looping step of looping the area dividing step, the decomposition coefficient determining step, and the equivalent number of atoms determining step in accordance with the determined equivalent atomic numbers of each point of the scanned object until the change of the decomposition coefficient based on the decomposition coefficients of all the points in all the divided areas is less than a predetermined one threshold.

In some embodiments of the present disclosure, the range subdivision includes:

Dividing all points located in an equal subinterval of a predetermined atomic number relation chain into an area corresponding to a position of an equivalent atomic number of each point of the scanned object in the atomic number relation chain, and materials corresponding to the atomic numbers at both end points of the subinterval are determined as base materials forming a base material combination of area.

In some embodiments of the present disclosure, the decomposition coefficient determination step includes for each of the divided regions
Calculating an integral of the decomposition coefficients of each point in the region along each path through which each ray passes, according to projection data of the beam having different energies, an energy spectrum of the region, and the damping coefficient functions corresponding to the base material combination of the region;
Determining decomposition coefficients of each point in the region according to the integral of the decomposition coefficients of each point in the region along each path through which each ray passes.

In some embodiments of the present disclosure, the energy spectrum of a region is determined according to an energy spectrum of a beam source, the decomposition coefficients of all points in other out-of-range regions, and the damping coefficient functions corresponding to the base material combinations of the other regions.

In some embodiments of the present disclosure, the equivalent atomic number determination step comprises:

Determining an equivalent electron density of each point in a divided region according to a decomposition coefficient of each point in the region and an atomic number and an atomic weight of all the base materials of the base material combination of the region;

Determining an equivalent atomic number of each point in the region according to the decomposition coefficient and the equivalent electron density of each point in the region and the atomic number and the atomic weight of all the base materials of the base material combination of the region.

In some embodiments of the present disclosure, the preserving step obtains the decomposition coefficients and the equivalent atomic numbers of all points of the scanned object according to a predetermined base material combination.

• dann, wenn die Änderung der Zerlegungskoeffizienten geringer ist als der vorgegebene Schwellenwert, Durchführen einer Substanzidentifikation für jeden der unterteilten Bereiche unter Verwendung der äquivalenten Atomzahl jedes Punkts in dem Bereich.

In some embodiments of the present disclosure, the method further comprises:

• when the change in the decomposition coefficients is less than the predetermined threshold, performing substance identification for each of the divided regions using the equivalent atomic number of each point in the region.

In some embodiments of the present disclosure, the dot includes a pixel dot or a voxel dot.

• einen Arbeitsspeicher; und
• einen Prozessor, der mit dem Arbeitsspeicher gekoppelt ist, wobei der Prozessor dazu konfiguriert ist, das Verfahren irgendeiner Ausführungsform auf der Basis von im Arbeitsspeicher gespeicherten Befehlen durchzuführen.

Another aspect of the present disclosure provides a decomposition apparatus based on a base material combination comprising:

• a working memory; and
• a processor coupled to the memory, wherein the processor is configured to perform the method of any embodiment based on instructions stored in memory.

Another aspect of the present disclosure provides a computer readable memory medium storing a computer program, the program being executed by a processor to implement the method of any embodiment.

In the present disclosure, a scanned object is divided into a plurality of regions, the base material combinations used in each of the divided regions are different from each other, and the scanned object is re-divided according to the newly determined equivalent atomic number of each point until the change of the Decomposition coefficient meets certain conditions. Thereby, a decomposition method based on dynamic base material combinations is realized, which reduces a decomposition error caused by improper selection of the base material combination, and improves the accuracy of decomposition and substance identification of the multi-energy CT. When the range of atomic number variation of the scanned object is large, such as. Medical CT-assisted imaging (using a contrast agent of a material such as iodine), high-energy or multi-energy CT imaging (such as safety, air-box or vessel CT imaging, etc.) The advantages are especially obvious.

list of figures

A brief introduction is given below for the drawings to be used in the description of the embodiments or related technologies. The present disclosure may be more clearly understood from the following detailed description with reference to the drawings.

• 1 ist ein Ablaufdiagramm einer Ausführungsform eines Zerlegungsverfahrens auf der Basis einer Basismaterialkombination der vorliegenden Offenbarung.
• 2 ist ein Ablaufdiagramm, das ein zyklisch ausgeführte Zerlegungsverfahren auf der Basis von dynamischen Basismaterialkombinationen zeigt, in dem die Gleichungen (6-13) an der Berechnung teilnehmen.
• 3 zeigt einen Satz von Simulationsversuchsergebnissen.
• 4 ist ein schematisches Strukturdiagramm einer Ausführungsform einer Zerlegungsvorrichtung auf der Basis einer Basismaterialkombination der vorliegenden Offenbarung.
• 5 ist ein schematisches Strukturdiagramm noch einer anderen Ausführungsform der Zerlegungsvorrichtung auf der Basis einer Basismaterialkombination der vorliegenden Offenbarung.

It will be understood that the drawings set forth below are merely some of the embodiments of the present disclosure. One skilled in the art could obtain other drawings from the accompanying drawings without any inventive effort.

• 1 FIG. 10 is a flowchart of one embodiment of a decomposition process based on a base material combination of the present disclosure. FIG.
• 2 Fig. 10 is a flowchart showing a cyclic decomposition method based on dynamic base material combinations in which equations (6-13) participate in the calculation.
• 3 shows a set of simulation trial results.
• 4 FIG. 12 is a schematic structural diagram of an embodiment of a base material combination-based decomposition apparatus of the present disclosure. FIG.
• 5 FIG. 12 is a schematic structural diagram of still another embodiment of the base material combination-disassembling apparatus of the present disclosure. FIG.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The inventor has found that the related decomposition method based on a solid base material combination has a good effect when the substance to be identified has a small range of atomic number variation, but a large decomposition error occurs when the range of atomic number variation is large. For example, damping coefficient functions of a substance whose range is the atomic number of carbon (atomic number Z = 6 representing organic matter) to lead (Z = 82 which is a heavy metal) are quite different. When a fixed set of base materials is used, for example, when carbon (Z = 6) and tin (Z = 50) are selected, the decomposition error of substances with Z> 50 and near Z = 28 in the scanned object is very large; if carbon (Z = 6) and lead (Z = 82) are selected, the decomposition error of substances with 30 <Z <60 in the scanned object is very large; when tin (Z = 50) and lead (Z = 82) are selected, the decomposition error of substances with Z <50 in the scanned object is very large.

A technical problem to be solved by the present disclosure is to reduce a decomposition error caused by improper selection of the base material combination.

The technical solutions in the embodiments of the present disclosure will be described in a clear and complete manner with reference to the accompanying drawings in the embodiments of the present disclosure.

1 FIG. 10 is a flowchart of one embodiment of a decomposition process based on a base material combination of the present disclosure. FIG. As in 1 As shown, the method of this embodiment includes the steps 100 - 140 ,

In step 100 , which can be called the conservation step, can provide initial information such as. For example, decomposition coefficients and an equivalent atomic number of each point of a scanned object can be obtained.

The preservation step obtains the decomposition coefficients and the equivalent atomic numbers of all points of the scanned object according to a solid base material combination. That is, the decomposition coefficients and the equivalent atomic numbers of all the points of the scanned object can be determined according to the decomposition result on the basis of a solid base material combination. The solid base material combination-based decomposition method can be realized by referring to a decomposition method based on the solid double base materials in the prior art.

In step 110 , which may be called the area dividing step, the scanned object may be divided into a plurality of areas according to the equivalent atomic number of each point of the scanned object, the base material combinations used in each of the divided areas being different from each other and an area assuming a same base material combination.

The point is a pixel point or a voxel point. If the scanned object is not a single material, the scanned object is usually divided into several areas. If the processing speed of the computer is fast enough, each pixel or voxel point of the scanned object can be divided into at most one area. When a processing speed of the computer is limited, a plurality of dots in the scanned object whose difference in the equivalent atomic number is smaller than a predetermined amount can be divided into an area.

In step 120 , which may be called decomposition coefficient determination step or decomposition step, may be determined with respect to each of the divided areas decomposition coefficients of each point in the area based on the base material combination used in the area.

In step 130 , which may be called the determining step for equivalent atomic numbers, when the change of the decomposition coefficient based on the decomposition coefficients of all the points in all divided regions is not less than a predetermined threshold, with respect to each of the divided regions, equivalent atomic numbers for all the points in FIG divided area on the basis of the determined decomposition coefficients of all points in the divided area and atomic information of all the base materials of the base material combination used in the divided area.

The atomic information includes, for example, atomic number and atomic weight.

In step 140 , which may be called a looping step, the area dividing step, the decomposition coefficient determining step, and the equivalent atomic number determining step may be cyclically performed according to the determined equivalent atomic numbers of each point of the scanned object until the change of the decomposition coefficient becomes smaller based on the decomposition coefficients of all the points in all the divided areas is a predetermined threshold, which means that the decomposition coefficients of the regions converge.

For example, if a change in the decomposition coefficients of all points in a certain range is less than the predetermined threshold, the decomposition coefficients of the range are considered convergent.

The substance identification for each divided region may be performed by using the equivalent atomic number of each point in the region after the convergence. Then, when the change of the decomposition coefficients is less than the predetermined threshold value, the substance identification for each divided region may be performed using the equivalent atomic number of each point in the region.

In the above embodiment, a scanned object is divided into a plurality of areas, the base material combinations used in each of the divided areas are different from each other, and the scanned object is re-divided according to the re-determined equivalent atomic number of each of its points until the change of the decomposition coefficient meets certain conditions. Thereby, a decomposition method based on dynamic base material combinations is realized, which reduces a decomposition error caused by improper selection of the base material combination, and improves the accuracy of decomposition and substance identification of the multi-energy CT.

When the amount of atomic number variation of the scanned object is large, such as. Medical CT-assisted imaging (using a contrast agent of a material such as iodine), high-energy or multi-energy CT imaging (such as safety, air-box or vessel CT imaging, etc.) The advantages are especially obvious. And it has an important application value for clinical medical, safety, industrial non-destructive testing and other fields.

The decomposition method based on a base material combination of the present disclosure is not only applicable to the dual energy (energy spectrum) CT, but also applicable to the multi-energy CT when projection data can be detected by more energy spectrums such as energy. For example, three energy CT data or energy spectrum CT data based on multi-energy photon counting detectors. at Dual-energy CT uses each area a combination of dual base materials. In multi-energy CT, each area requires a combination of several base materials of the same number as the energy spectra. For example, in a three-energy CT, each area requires a combination of three base materials. The specific equations of the subsequent embodiment will be described using the dual energy CT as an example. According to the dual-base CT dual base material decomposition method of the present disclosure, those skilled in the art can obtain the multi-energy CT decomposing method without any creative work.

An exemplary implementation of step 120 is implemented using an iterative method. The iterative method comprises: starting from t = 1, calculating decomposition coefficients of each point in the area t based on a base material combination of the area t, and then taking the decomposition coefficients of each point in the area t as known parameters for the next calculation and calculating decomposition coefficients of each point in Range t + 1 based on a base material combination of the range t + 1 and terminate until t is increased to N to obtain decomposition coefficients of each point in each range, where N represents the number of ranges.

The calculation method of the decomposition coefficients of each point in a specific area t based on a base material combination of the area t includes: calculating an integral of the decomposition coefficients of each point in the area along each path through which each beam passes, according to projection data of the beam having different energies (such as B. high energy projection data and low energy projection data), an energy spectrum of the region and attenuation coefficient functions corresponding to the base material combination of the region; Determining decomposition coefficients of each point in the region with a predetermined reconstruction algorithm according to the integral of the decomposition coefficients of each point in the region along each path through which each ray passes. For example, the reconstruction algorithm may be a filtered backprojection (FBP) algorithm.

The calculation method of the decomposition coefficients of each point in a specific range t on the basis of a base material combination of the region t will be described by taking the combination of the double base materials as an example in the present embodiment, and may be particularly described with reference to the equations (1-10). be implemented.

Assume that the scanned object is divided into N areas expressed as: $${\mathrm{\Omega }}_1.{\mathrm{\Omega }}_2.....{\mathrm{\Omega }}_N$$

wobei j die Nummer eines unterschiedlichen Bereichs ist.Attenuation coefficient functions of the dual base materials used in each range are: $${\mu }_1\left(j.e\right).{\mu }_2\left(j.e\right).j=1.2....N$$

where j is the number of a different area.

The decomposition coefficients (or decomposition coefficient image) of each dot (pixel dot or voxel dot) based on double base materials are recorded as: $$b_1\left(x\right).b_2\left(x\right)$$

Where x represents a pixel point or a voxel point.

$$\text{wobei }{b}_k^j\left(x\right)=\{\begin{array}{r}\hfill b_k\left(x\right),x\in {\mathrm{\Omega }}_j\\ \hfill \mathrm{0,}x\notin {\mathrm{\Omega }}_j\end{array},k=\mathrm{1,2}$$

Then, the projection data of an X-ray with high (H) / low (L) energy can be written in the X-ray dual energy CT as: $$p_{L\text{/}H}\left(ra{y}_I\right)={\displaystyle {\int }_0^{e_{\text{Max}}^{L\text{/}H}}{S}_{L\text{/}H}}\left(e\right)\text{exp}\left(-{\displaystyle {\int }_{ra{y}_I}\left[{\displaystyle \underset{j=1}{\overset{N}{\Sigma }}{b}_1^j\left(x\right){\mu }_1\left(j.e\right)+b_2^j\left(x\right){\mu }_2\left(j.e\right)}\right]dI}\right)de$$

$$\text{in which}{b}_k^j\left(x\right)=\{\begin{array}{r}\hfill b_k\left(x\right).x\in {\mathrm{\Omega }}_j\\ \hfill 0x\notin {\mathrm{\Omega }}_j\end{array}.k=1.2$$

stellt eine maximale Energie des Energiespektrums einer Strahlquelle mit hoher/niedriger Energie dar, ray₁ stellt einen Weg dar, durch den der i-te Strahl verläuft, und ein Integral von dl in Gleichung (4) ist ein Integral der relevanten physikalischen Größen entlang des Weges, durch den der Strahl verläuft.S _{L / H} (E) represents the energy spectrum of a high / low power beam source, ${\text{e}}_{\text{Max}}^{\text{L / H}}$

represents a maximum energy of the energy spectrum of a high / low power beam source, ray ₁ represents a path through which the i-th beam passes, and an integral of dl in equation (4) is an integral of the relevant physical quantities along the Path through which the beam passes.

wobei $${\tilde{S}}_{L\text{/}H}\left(E\right)=S_{L\text{/}H}\left(E\right)\text{exp}\left(-{\displaystyle {\int }_{ra{y}_i}\left[{\displaystyle \sum _{j=1j\ne t}^N{b}_1^j\left(x\right){\mu }_1\left(j,E\right)+b_2^j\left(x\right){\mu }_2\left(j,E\right)}\right]dl}\right)$$

"T" represents the currently dissolved area. Assume that the decomposition coefficient image of the areas other than the area t is known. The decomposition coefficient image of the region t can be obtained by the foregoing decomposition method, it can be learned from the dual energy projection equation (4) that: $$\{\begin{array}{c}{p}_L\left(ra{y}_i\right)={\displaystyle {\int }_0^{e_{\text{Max}}^L}{\tilde{S}}_L\left(e\right)\text{exp}(-{\mu }_1\left(t.e\right){\displaystyle {\int }_{ra{y}_i}{b}_1\left(x.t\right)dl-{\mu }_2\left(t.e\right){\displaystyle {\int }_{ra{y}_i}{b}_2\left(x.t\right)dl)de}}}\\ p_H\left(ra{y}_i\right)={\displaystyle {\int }_0^{e_{\text{Max}}^{II}}{\tilde{S}}_H\left(e\right)\text{exp}(-{\mu }_1\left(t.e\right){\displaystyle {\int }_{ra{y}_i}{b}_1\left(x.t\right)dl-{\mu }_2\left(t.e\right){\displaystyle {\int }_{ra{y}_i}{b}_2\left(x.t\right)dl)de}}}\end{array}$$

in which $${\tilde{S}}_{L\text{/}H}\left(e\right)=S_{L\text{/}H}\left(e\right)\text{exp}\left(-{\displaystyle {\int }_{ra{y}_i}\left[{\displaystyle \underset{j=1j\ne t}{\overset{N}{\Sigma }}{b}_1^j\left(x\right){\mu }_1\left(j.e\right)+b_2^j\left(x\right){\mu }_2\left(j.e\right)}\right]dl}\right)$$

j = 1,2,..., N, j ≠ t der anderen Bereiche als des Bereichs t bekannt sind, und da S_L/H (E) auch bekannt ist, kann ein Energiespektrum des Bereichs S̃_L/H (E) berechnet werden, wodurch ein Integral des Zerlegungskoeffizientenbildes des Bereichs t entlang des Weges, durch den der Strahl ray_i verläuft, durch die Dualenergie-Projektionsgleichung (6) berechnet werden kann, das heißt: $$B_1\left(ra{y}_i\right)={\displaystyle {\int }_{ra{y}_i}{b}_1\left(x,t\right)dl,B_2\left(ra{y}_i\right)={\displaystyle {\int }_{ra{y}_i}{b}_2\left(x,t\right)dl}}$$

Since the decomposition coefficient images $b_1^j.b_2^j.$

j = 1,2, ..., N, j ≠ t of the regions other than the region t are known, and since S _{L / H} (E) is also known, an energy spectrum of the region S _{L / H} (E) whereby an integral of the decomposition coefficient image of the region t along the path through which the ray ray _i passes can be calculated by the dual energy projection equation (6), that is, $$B_1\left(ra{y}_i\right)={\displaystyle {\int }_{ra{y}_i}{b}_1\left(x.t\right)dl.B_2\left(ra{y}_i\right)={\displaystyle {\int }_{ra{y}_i}{b}_2\left(x.t\right)dl}}$$

The decomposition coefficients of each pixel / voxel point may be reconstructed with a general CT reconstruction algorithm (such as FBP algorithm) according to the integral of the decomposition coefficient image of the region along each path through which each ray passes, that is: $$b_1\left(x.t\right)=\text{Recon}\left\{B_1\left(Ra{y}_i\right)|i\right\}.b_2\left(x.t\right)=\text{Recon}\left\{B_2\left(ra{y}_i\right)|i\right\}$$

Where Recon is a reconstruction algorithm.

Since it is limited to the range t, the final decomposition coefficient image is expressed as: $$b_k\left(x\right)=\{\begin{array}{r}\hfill b_k\left(x.t\right).x\in {\mathrm{\Omega }}_t\\ \hfill b_k\left(x\right).x\notin {\mathrm{\Omega }}_t\end{array}.k=1.2$$

An exemplary method for determining an equivalent atomic number of each point in the specific area in step 130 comprising: determining an equivalent electron density of each point in a divided region according to a decomposition coefficient of each point in the region and an atomic number and an atomic weight of all the base materials of the base material combination of the region; Determining an equivalent atomic number of each point in the region according to the decomposition coefficient and the equivalent electron density of each point in the region and the atomic number and the atomic weight of all the base materials of the base material combination of the region.

Taking the combination of dual base materials as an example, the equations of calculation of the equivalent electron density ρ _eff and the equivalent atomic number Z _{eff of} each point are as follows: $$\begin{array}{l}{\rho }_{eff}\left(x\right)=b_1\left(x\right)\frac{Z_1^j}{A_1^j}+b_2\left(x\right)\frac{Z_2^j}{A_2^j}.x\in {\mathrm{\Omega }}_j\hfill \\ Z_{eff}\left(x\right)={\left[\left(b_1\left(x\right)\frac{{\left(Z_1^j\right)}^{\alpha }}{A_1^j}+b_2\left(x\right)\frac{{\left(Z_2^j\right)}^{\alpha }}{A_2^j}\right)/{\rho }_{eff}\left(x\right)\right]}^{1\text{/}\left(\alpha -1\right)}.x\in {\mathrm{\Omega }}_j\hfill \end{array}$$

ausgedrückt werden und die Atomgewichte der doppelten Basismaterialien als $A_1^j\text{ und }{A}_2^j$

ausgedrückt werden.Where the atomic numbers of the double base materials used in the region j, as $Z_1^j\text{and}{Z}_2^j$

and the atomic weights of the double base materials as $A_1^j\text{and}{A}_2^j$

be expressed.

Wherein the parameter α is determined empirically, as follows: $$\{\begin{array}{c}\alpha =\mathrm{05/04,}\text{Max}\left(Z_1^j.Z_2^j\right)\le 50\\ \alpha =\mathrm{2,}\text{Max}\left(Z_1^j.Z_2^j\right)>50\end{array}$$

An exemplary area division method of the scanned object in step 110 comprising: dividing all points located in an equal subinterval of a predetermined atomic number relationship chain into an area corresponding to a position of an equivalent atomic number of each point of the scanned object in the atomic number relation chain, and materials corresponding to the atomic numbers at both endpoints of the subinterval are referred to as Determines base materials that form a base material combination of the region.

A length (that is, the size of N in Equation 13) of the atomic number relation chain is related to the accuracy of the substance identification. The larger the length of the atomic number relation chain, the more areas the object is subdivided, the higher the accuracy of the substance identification. For example, with respect to the atomic numbers used to delineate the boundary of the region in the atomic number relation chain, atomic numbers corresponding to common materials may be selected, or they may be determined according to the materials contained in the detected object.

The equation for the foregoing area dividing method is expressed as follows: $$\begin{array}{l}6=Z_0<Z_1<Z_2<...<Z_{N-1}<Z_N=80\\ {\mathrm{\Omega }}_j=\left[x|Z_{j-1}\le Z_{eff}\left(x\right)<Z_j\right]\end{array}$$

entspricht.The dual base materials in the newly divided region may be selected as materials to which $Z_1^j=Z_{j-1}.Z_2^j=Z_j$

equivalent.

As described above, a decomposition method based on dynamic base material combinations of the present disclosure is cyclically performed before the decomposition coefficients of all regions converge. 2 FIG. 13 is a flowchart showing a cyclic decomposition method based on dynamic base material combinations in which equations (6-13) participate in the computation, where Eq. represents an equation, for example Eq. (10) represents Equation 10.

3 shows a set of simulation trial results. The image size is 256 * 256, the pixel size is 1.6mm * 1.6mm, the number of detector units is 736, the number of rotation angles is 540, and the rotation angle is 360 °. The highest energy of the dual energy CT beam source energy spectrum is 9 MeV or 6 MeV. The material of the large cylinder in the model is water and the other small cylinders are divided into inner and outer groups. The inner and outer groups have the same materials and the atomic numbers of the materials are: 13, 20, 26, 30, 34, 40, 50, 60, 70, 80 (counterclockwise rotation, color from shallow to deep). The three pictures in 3 from left to right in order are: a real atomic number image, an atomic number image obtained by a conventional decomposition method based on solid double base materials using materials having atomic numbers of 6 and 50 as solid double base materials, and an atomic number image by the decomposition method based on dynamic base material combinations of the present disclosure. From the simulation results, it can be seen that the present disclosure can effectively improve the decomposition accuracy of the X-ray dual energy CT, can reduce the decomposition error caused by inconsistency of materials between a dual-energy CT imaging model and the physical process, and a important meaning and an important application value for improving the imaging quality and substance identification accuracy of dual-energy CT has.

The present disclosure also proposes a decomposition apparatus based on a base material combination comprising: one or more modules for performing the foregoing decomposition method.

4 FIG. 12 is a schematic structural diagram of one embodiment of a base material combination-based decomposition apparatus according to the present disclosure. FIG.

As in 4 The cutting device comprises a basis material combination 40 : Modules 400 - 440 ,

The conservation module 400 is configured to obtain decomposition coefficients and an equivalent atomic number of each point of a scanned object.

The area subdivision module 410 is configured to divide the scanned object into a plurality of regions according to the equivalent atomic number of each point of the scanned object, and the base material combinations used in each of the divided regions are different from each other.

The decomposition coefficient determination module 420 is configured to determine decomposition coefficients of each point in the area with respect to each of the divided areas based on the base material combination used in the area.

The determination module 430 for equivalent atomic numbers is for determining equivalent atomic numbers for all points in the divided region with respect to each of the divided regions on the basis of the determined decomposition coefficients of all points in the divided region and atomic information of all base materials of the base material combination used in the divided region if the change in the decomposition coefficient based on the decomposition coefficients of all the points in all the divided areas is not less than a predetermined threshold value.

The loop pass module 440 is configured to loop through the area dividing step, the decomposition coefficient determining step, and the equivalent atomic number determining step according to the determined equivalent atomic numbers of each scanned object point until the change of the decomposition coefficient based on the decomposition coefficients of all the points in all the divided areas is less than a predetermined one threshold.

Optionally, the decomposition coefficients and the equivalent atomic numbers of all points of the scanned object required at the beginning of the cycle are determined according to a given (fixed) base material combination. Optionally, the area subdivision module 410 for dividing all dots arranged in an equal sub-interval of a predetermined atomic number relation chain into a region corresponding to a position of an equivalent atomic number of each point of the scanned object in the atomic number relation chain, and materials corresponding to the atomic numbers at both end points of the subinterval are used as base materials intended to form a base material combination of the area.

Optionally, the decomposition coefficient determination module is 420 configured to implement using an iterative method. The iterative method comprises: starting from t = 1, calculating decomposition coefficients of each point in the region t based on a material combination of the region t, and then taking the decomposition coefficients of each point in the region t as known parameters for the next calculation and calculating decomposition coefficients of each point in the region t + 1 on the basis of a base material combination of the region t + 1 and terminating until t is increased to N To obtain decomposition coefficients of each point in each area, where N represents the number of areas.

Optionally, the calculation method includes the decomposition coefficients of each point in a specific area t based on a base material combination of the area t: calculating an integral of the decomposition coefficients of each point in the area along each path through which each beam passes, according to projection data of the beam having different energies (such as eg, high energy projection data and low energy projection data), an energy spectrum of the region, and attenuation coefficient functions corresponding to the base material combination of the region; Determining decomposition coefficients of each point in the region with a predetermined reconstruction algorithm according to the integral of the decomposition coefficients of each point in the region along each path through which each ray passes. For example, the reconstruction algorithm may be a filtered backprojection (FBP) algorithm. Optionally, the determination module 430 for equivalent atomic numbers for determining an equivalent electron density of each point in a divided region according to a decomposition coefficient of each point in the region and an atomic number and an atomic weight of all the base materials of the base material combination of the region and for determining an equivalent atomic number of each point in the region according to the decomposition coefficient and equivalent electron density of each point in the region and the atomic number and the atomic weight of all the base materials of the base material combination of the region configured.

5 FIG. 12 is a schematic structural diagram of still another embodiment of the base material combination-disassembling apparatus of the present disclosure. FIG.

As in 5 The cutting device comprises a basis material combination 50 a working memory 510 and a processor 520 that with the memory 510 is coupled. The processor 520 is configured to perform the decomposition method in any of the foregoing embodiments on the basis of in-memory 510 to execute stored commands.

The working memory 510 For example, it may include a system memory, a fixed nonvolatile storage medium, or the like. For example, the system memory stores an operating system, an application, a bootloader, and other programs.

The device 50 can also have an input / output interface 530 , a network interface 540 , a storage interface 550 and the like. These interfaces 530 . 540 . 550 , the working memory 510 and the processor 520 for example, via a bus 560 be connected. The input / output interface 530 sees a connection interface for input / output devices such. For example, a display, a mouse, a keyboard and a touch screen. The network interface 540 provides a connection interface for various networked devices. The storage interface 550 sees a connection interface for external storage devices such. For example, SD cards and USB flash drives.

The present disclosure also provides a computer-readable storage medium storing a computer program, the program being executed by a processor to implement the decomposition method of any of the foregoing embodiments.

It should be understood by those skilled in the art that embodiments of the present disclosure may be provided as a method, system, or computer program product. Thus, the present disclosure may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment that combines both software and hardware. Moreover, the present disclosure may take the form of a computer program product implemented on one or more computer usable non-transitory storage media (including, but not limited to, a disk storage, CD-ROM, optical storage, etc.) having computer usable program code therein.

The above are only the preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Any modification, equivalent substitution, enhancement, etc., within the spirit and principles of the present disclosure should be covered within the scope of the present disclosure.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• CN 201711432840 [0001]

Claims (10)

Dismantling method based on a base material combination, comprising: a preserving step for obtaining decomposition coefficients and an equivalent atomic number of each point of a scanned object; a region dividing step for dividing the scanned object into a plurality of regions according to the equivalent atomic number of each point of the scanned object, the base material combinations used in each of the divided regions being different from each other; a decomposition coefficient determination step for determining decomposition coefficients of each point in the region with respect to each of the divided regions based on the base material combination used in the region; an equivalent atomic number determining step for determining equivalent atomic numbers for all the divided region points with respect to each of the divided regions based on the determined decomposition coefficients of all the divided region points and atomic information of all the base material combination base materials used in the divided region, then when the change of the decomposition coefficient based on the decomposition coefficients of all points in all the divided areas is not less than a predetermined threshold; and a looping step of traversing the area dividing step, the decomposition coefficient determining step, and the equivalent atomic number determining step according to the determined equivalent atomic numbers of each point of the scanned object until the change of the decomposition coefficient based on the decomposition coefficients of all the points in all the divided areas is less than a predetermined threshold value. Method according to Claim 1 wherein the area dividing step comprises dividing all the dots arranged in a same subinterval of a predetermined atomic number relation chain into an area corresponding to a position of an equivalent atomic number of each point of the scanned object in the atomic number relation chain, materials corresponding to the atomic numbers at both endpoints of the atomic number relationship Subinterval correspond to be determined as base materials that form a base material combination of the area. Proceed according to either Claim 1 or Claim 2 wherein the decomposition coefficient determination step comprises: for each of the divided regions, computing an integral of the decomposition coefficients of each point in the region along each path through which each ray passes, according to projection data of the beam having different energies, an energy spectrum of the region, and attenuation coefficient functions corresponding to the base material combination of the region correspond; Determining decomposition coefficients of each point in the region according to the integral of the decomposition coefficients of each point in the region along each path through which each ray passes. Method according to one of Claims 1 to 3 wherein the energy spectrum of a region is determined according to an energy spectrum of a beam source, the decomposition coefficients of all points in other regions outside the region, and the damping coefficient functions corresponding to the base material combinations of the other regions. Method according to one of Claims 1 to 4 wherein the equivalent atomic number determining step comprises: determining an equivalent electron density of each dot in a divided region according to a decomposition coefficient of each dot in the region and an atomic number and an atomic weight of all the base materials of the base material combination of the region; Determining an equivalent atomic number of each point in the region according to the decomposition coefficient and the equivalent electron density of each point in the region and the atomic number and the atomic weight of all the base materials of the base material combination of the region. Method according to one of Claims 1 to 5 wherein the preserving step obtains the decomposition coefficients and the equivalent atomic numbers of all points of the scanned object according to a predetermined base material combination. Method according to one of Claims 1 to 6 further comprising, when the change in the decomposition coefficients is less than the predetermined threshold, performing substance identification for each divided region using the equivalent atomic number of each point in the region. Method according to one of Claims 1 to 7 , where the dot comprises a pixel point or a voxel point. A base material combination-based decomposing apparatus comprising: a work memory; and a processor coupled to the memory, wherein the processor is configured to perform the method according to any one of Claims 1 - 8th based on instructions stored in memory. A computer readable storage medium storing a computer program, the program being executed by a processor to perform the method of any one of Claims 1 - 8th to implement.

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